Hexagon: add support for single-stepping (v4+)

Hardware single-step is only available on v4 and later
architectures.

Signed-off-by: Richard Kuo <rkuo@codeaurora.org>

6 files changed, 38 insertions, 1 deletions

diff --git a/arch/hexagon/include/uapi/asm/ptrace.h b/arch/hexagon/include/uapi/asm/ptrace.h
index 1ffce0c6ee07..065e5b32313f 100644
--- a/arch/hexagon/include/uapi/asm/ptrace.h
+++ b/arch/hexagon/include/uapi/asm/ptrace.h
@@ -36,4 +36,9 @@ extern const char *regs_query_register_name(unsigned int offset);
         ((struct pt_regs *) \
          ((unsigned long)current_thread_info() + THREAD_SIZE) - 1)
 
+#if CONFIG_HEXAGON_ARCH_VERSION >= 4
+#define arch_has_single_step()  (1)
+#endif
+
+
 #endif
diff --git a/arch/hexagon/include/uapi/asm/registers.h b/arch/hexagon/include/uapi/asm/registers.h
index 80504155ca3a..fcdb5f96a984 100644
--- a/arch/hexagon/include/uapi/asm/registers.h
+++ b/arch/hexagon/include/uapi/asm/registers.h
@@ -211,6 +211,9 @@ struct pt_regs {
 #define pt_psp(regs) ((regs)->hvmer.vmpsp)
 #define pt_badva(regs) ((regs)->hvmer.vmbadva)
 
+#define pt_set_singlestep(regs) ((regs)->hvmer.vmest |= (1<<HVM_VMEST_SS_SFT))
+#define pt_clr_singlestep(regs) ((regs)->hvmer.vmest &= ~(1<<HVM_VMEST_SS_SFT))
+
 #define pt_set_rte_sp(regs, sp) do {\
         pt_psp(regs) = (sp);\
         (regs)->SP = (unsigned long) &((regs)->hvmer);\
diff --git a/arch/hexagon/kernel/ptrace.c b/arch/hexagon/kernel/ptrace.c
index 3982d9c9ec2b..70df50d797d8 100644
--- a/arch/hexagon/kernel/ptrace.c
+++ b/arch/hexagon/kernel/ptrace.c
@@ -32,6 +32,21 @@
 
 #include <asm/user.h>
 
+#if arch_has_single_step()
+/*  Both called from ptrace_resume  */
+void user_enable_single_step(struct task_struct *child)
+{
+        pt_set_singlestep(task_pt_regs(child));
+        set_tsk_thread_flag(child, TIF_SINGLESTEP);
+}
+
+void user_disable_single_step(struct task_struct *child)
+{
+        pt_clr_singlestep(task_pt_regs(child));
+        clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+}
+#endif
+
 static int genregs_get(struct task_struct *target,
                    const struct user_regset *regset,
                    unsigned int pos, unsigned int count,
diff --git a/arch/hexagon/kernel/traps.c b/arch/hexagon/kernel/traps.c
index 12164a30e8ff..c2eeeef55335 100644
--- a/arch/hexagon/kernel/traps.c
+++ b/arch/hexagon/kernel/traps.c
@@ -451,3 +451,14 @@ void do_machcheck(struct pt_regs *regs)
         /* Halt and catch fire */
         __vmstop();
 }
+
+/*
+ * Treat this like the old 0xdb trap.
+ */
+
+void do_debug_exception(struct pt_regs *regs)
+{
+        regs->hvmer.vmest &= ~HVM_VMEST_CAUSE_MSK;
+        regs->hvmer.vmest |= (TRAP_DEBUG << HVM_VMEST_CAUSE_SFT);
+        do_trap0(regs);
+}
diff --git a/arch/hexagon/kernel/vm_entry.S b/arch/hexagon/kernel/vm_entry.S
index 053551ee7114..9add73ab57d8 100644
--- a/arch/hexagon/kernel/vm_entry.S
+++ b/arch/hexagon/kernel/vm_entry.S
@@ -367,6 +367,9 @@ _K_enter_trap0:
 _K_enter_machcheck:
         vm_event_entry(do_machcheck)
 
+        .globl _K_enter_debug
+_K_enter_debug:
+        vm_event_entry(do_debug_exception)
 
         .globl ret_from_fork
 ret_from_fork:
diff --git a/arch/hexagon/kernel/vm_vectors.S b/arch/hexagon/kernel/vm_vectors.S
index 620f42cc582a..aff4054a2cff 100644
--- a/arch/hexagon/kernel/vm_vectors.S
+++ b/arch/hexagon/kernel/vm_vectors.S
@@ -41,7 +41,7 @@ _K_VM_event_vector:
         jump 1b;  /*  Reset  */
         jump _K_enter_machcheck;
         jump _K_enter_genex;
-        jump 1b;  /*  3 Rsvd  */
+        jump _K_enter_debug;
         jump 1b;  /*  4 Rsvd  */
         jump _K_enter_trap0;
         jump 1b;  /*  6 Rsvd  */